The invention relates generally to liquid petroleum gas (LPG) fuel injectors and injection systems for devices such as furnaces, water heaters and engines and specifically to a direct injection fuel system that eliminates the need for regulators, vaporizers, lock-out valves, carburetors, transfer pumps and the like and that injects LPG fuel in a liquified state into an air/fuel mixing chamber of such devices.
Liquid petroleum gas has been used in a variety of combustion systems such as stoves, furnaces, water heaters and internal combustion engines. The common feature of these various LPG combustion systems is the reduction of the LPG from a high pressure liquified state to a low pressure gasified state and no thereafter mix the low pressure previously vaporized gas with air. These systems require a sophisticated progression of components such as: solenoids, lock-off valves, pressure regulators, vaporizers and carburetors or mixers increasing the cost and lowering the reliability of the fuel system.
LPG is a mixture of light petroleum hydrocarbons and when stored under a moderate pressure reduces to a liquid and when released to the atmosphere at normal ambient temperatures rapidly vaporizes to a gas. This feature represents a significant difference in comparing LPG to other fuels such as gasoline, kerosene, alcohol and diesel fuel.
As mentioned above the basic components of existing LPG gasified carburetion systems include: a pressurized fuel tank from which the LPG passes in a liquified state through a filter and to a solenoid lock-off valve. The liquid fuel is fed from the lock-out valve into a pressure regulator-vaporizer which comprises a two or three stage regulator dropping the pressure of the LPG to nearly atmospheric pressure at which point it is reduced to a vapor. This characteristic requires the supplying of heat to the regulator-vaporizer to maintain the LPG in its vaporous state. The LPG vapor (gas) is fed to a carburetion device such as a carburetor or mixer where it is mixed with air.
An advantage of the present system as compared with the presently available LPG carburetion systems is the elimination of costly devices such as a carburetor, pressure regulator, vaporizer lock-out valve. In addition a further advantage of the present invention as compared to conventional gasoline or diesel systems is the elimination of a fuel or transfer pump to transport fuel from a storage tank to a fuel injector. A most important advantage of the present invention is providing means for correcting the activation signal to the fuel injector to compensate for pressure and density variations in the LPG fuel. A further advantage of the present invention is that it provides that the endothermic expansion of the liquid LPG to a vapor occur while the expanding fuel is mixing with the induced air. The power output of almost all fuel systems for internal combustion engines is that they are air limited. Consequently, if more air is introduced into the combustion chamber (engine) performance is enhanced. If the air that is introduced into the combustion chamber is cooled the extent of certain noxious exhaust emissions is lowered. By causing the endothermic expansion of the LPG to occur as described the induced air is cooled, made more dense and hence more air molecules are introduced into the combustion chamber yielding improved performance. Further lowering the temperature will decrease a spark ignited engine's tendency to pre-ignite and knock.
Accordingly, the present invention is directed to a fuel injection system for injecting liquified petroleum gas (LPG) into at least one air/fuel mixing chamber from a storage means such as a fuel tank, that stores pressurized LPG in its liquid state. In one embodiment, the fuel system includes injection means adapted to receive pressurized LPG from the storage means for selectively delivering the LPG to the air/fuel mixing chamber in its liquified state. The injection means, may include an electromagnetic fuel injector including first means for providing that the endothermic expansion of the LPG from its liquid to its vapor state occur at or beyond the lower extreme of the body. In another embodiment the fuel system includes means for compensating for fuel metering errors arising from pressure and density variations of the LPG fuel within the system.
Many other objects, features and advantages of the invention will be clear from the following detailed description of the drawings.